JSONParseAsync.js

function JSONParseAsync( text, callback ) {

	var code = 'onmessage = function ( e ) { postMessage( JSON.parse( e.data ) ); close(); }';
	var blob = new Blob( [ code ], { type: 'text/plain' } );
	var worker = new Worker( window.URL.createObjectURL( blob ) );
	worker.addEventListener( 'message', function ( e ) { callback( e.data ); } );
	worker.postMessage( text );

}

// Chrome 42+, Firefox 39+, Safari 10.1+
function JSONParseAsync( string ) {
	return ( new Response( string ) ).json(); // Returns Promise
}